Fatigue fracture of a garden tool

The tool made of ferritic construction steel (hardness 169 HV0.3, converted to 542 MPa tensile strength, i.e. possibly S355) could not withstand clay soil and dandelion roots in the long run and finally succumbed to a fatigue fracture under double-sided bending. In the center of the fracture surface, between the two massively hammered vibration cracks (low cycle fatigue?), only a strip approx. 100 µm wide remained for ductile final overload fracture.